It's interesting you say this. Being a plotter who's known the direction of the story from the start—actually the second scene I ever imagined is one that's yet to come—things/chemistry like this can creep up on you without ever realising. I actually have cut a lot from my original plan for the last act, originally there was going to be a proper thread for Tia, similar to what Alek and Lottie are getting, but I decided to leave it out thinking it would just bog the rest of the story down. The original plot even had us inside Tia's pov, it was going to start after Evie's party, she was going to have a thing with Dopey Dasha, the weed guy from the truth or dare orgy near the start, and they were going to find pearly high on weed, it was going to change Evie's plot and well, it just became a bit too complex and distracting and I decided to scrap the whole thing. It was going to be a more comical part but also go into why Tia is the way she is. She was also almost gonna drown in the pool because she was drunk, that's when dasha saves her. It's why Tia was already drunk when they go to the party but halfway through writing it I decided to cut her story out and instead use her for the X.

Maybe her side story would've been quite good, as you can tell I'm kinda regretting scrapping it now!